Scanning systems receive radiation, typically light, from an object through an imaging aperture for transforming the radiation into electrical signals for possible storage and/or reproduction of the image of the object onto some medium. The system scans the objective in some pattern, such as a raster scan, so that the imaging aperture sequentially receives radiation from the entire field of view.
FIG. 1 symbolically represents an exemplary scanning system. As shown in the drawing, a scanning head 14 reads the images of objects on a paper sheet 11 for reproduction of the images upon a second sheet of paper 13. The object is the letter "a". The scanning head 14 has a photodetector, in this case, a photoelectric transistor 16 which is sensitive to the light reflected off the sheet 11 and the image 10. In this example, the light is generated by a light emitting diode (LED) 15, which is also mounted to the scanning head 14. Not shown is a scanning mechanism which drives the scanning head 14 with respect to the sheet 11. As the scanning head 14 moves across the sheet 11 in one direction (and is stepped in a direction perpendicular to the first direction after each line of scanning in the first direction is completed), the phototransistor 16 reacts to the amount of reflected light, i.e., whether the scanned area is light or dark. This sequence of signals is received by a processing circuit 18 for conditioning the signals to power a thermal print head 21. The thermal print head 21 has a heating element 20 to reproduce an image 12 on a sheet 13 of thermally sensitive paper of the object 10. A power supply block 17 supplies the required voltage and currents to the LED 15 and the signal processing block 18.
A problem with all scanning systems is that the aperture through which radiation from the object is received is necessarily of a finite size. Ideally, the size of the aperture should be inifinitely small so that the image of the object is scanned point-by-point. Without an infinitely small aperture, the image of the scanned object is distorted. This degrades the resolution of the scanning system.
Prior efforts to improve the resolution of appertures in scanning systems have used optical components, such as lenses, optical fibers, mirrors, and prisms, to create a focused image of the object received by the scanning system. However, these components require particular attention to their shapes and the relative positioning of the components between themselves and the photodetector. All these concerns add to the cost of the scanning system.
The present invention provides for an efficient and economical way of increasing the scanning resolution of the scanning aperture without the use of optical components.